geez that sucks man, cos ive got the same issue with my car after i changed the headers on my 1zz, i noticed the yellow indicator light come on too. i took it to toyota to do a diagnostic, and they said it was also an 02 sensor issue, and said it was no problem to drive around with. so ive been driving around with it for the last 9 months..without any issue. i too am looking for a solution ><